Wheelchairs are now in wide use, and various types have been heretofore suggested, including wheelchairs powered by electrical drive units.
Various types of control systems have been heretofore suggested for controlling application of drive to the wheels of a powered wheelchair, with a joy-stick being often utilized as the control actuator to be manipulated by the user.
While joy-stick type controls for powered wheelchairs have extended self-propelled use of wheelchairs to some severely handicapped persons, such powered wheelchairs have not proved to be entirely satisfactory for use by at least some groups of potential users, including, for example, persons having sufficient use of their hands and/or arms to enable that user to at least partially manually propel the wheelchair by application of force to the hand rims connected to the main wheels thus affording the user satisfaction and/or exercise. In addition, powered wheelchairs are most often quite heavy and/or cumbersome, and joy-stick type controlled power wheel chairs have been found by at least some users to be more difficult to maneuver in close quarters.
Wheelchairs have also heretofore been configured so as to be foldable, or collapsible, to facilitate transporting and/or storage, and some such wheel chairs have been provided with power units at least some components of which have been removable (see, for example U.S. Pat. Nos. 3,770,073 and 3,064,744).
A power-assisted wheelchair for use by a partially disabled person having sufficient use of hands and/or arms to enable some application of force to the hand rims of the wheelchair to cause energization of electric motors by sensing displacement of the hand rims relative to the drive wheel has been heretofore suggested (see U.S. Pat. Nos. 4,050,533, 4,125,169 and 4,422,515). Such wheelchairs, however, have not proved to be entirely satisfactory, and improvements in such wheelchairs are therefore still desired and/or needed.